The development of the tetracycline antibiotics was the direct result of a systematic screening of soil specimens collected from many parts of the world for evidence of microorganisms capable of producing bacteriocidal and/or bacteriostatic compositions. The first of these novel compounds was introduced in 1948 under the name chlortetracycline. Two years later, oxytetracycline became available. The elucidation of the chemical structure of these compounds confirmed their similarity and furnished the analytical basis for the production of a third member of this group in 1952, tetracycline. A new family of tetracycline compounds, without the ring-attached methyl group present in earlier tetracyclines, was prepared in 1957 and became publicly available in 1967.
Recently, research efforts have focused on developing new tetracycline antibiotic compositions effective under varying therapeutic conditions and routes of administration. New tetracycline analogues have also been investigated which may prove to be equal to or more effective than the originally introduced tetracycline compounds. Examples include U.S. Pat. Nos. 3,957,980; 3,674,859; 2,980,584; 2,990,331; 3,062,717; 3,557,280; 4,018,889; 4,024,272; 4,126,680; 3,454,697; and 3,165,531. These patents are representative of the range of pharmaceutically active tetracycline and tetracycline analogue compositions.
Historically, soon after their initial development and introduction, the tetracyclines were found to be highly effective pharmacologically against rickettsiae; a number of gram-positive and gram-negative bacteria; and the agents responsible for lymphogranuloma venereum, inclusion conjunctivitis, and psittacosis. Hence, tetracyclines became known as xe2x80x9cbroad spectrumxe2x80x9d antibiotics. With the subsequent establishment of their in vitro antimicrobial activity, effectiveness in experimental infections, and pharmacological properties, the tetracyclines as a class rapidly became widely used for therapeutic purposes. However, this widespread use of tetracyclines for both major and minor illnesses and diseases led directly to the emergence of resistance to these antibiotics even arnong highly susceptible bacterial species both commensal and pathogenic (e.g., pneumococci and Salmonella). The rise of tetracycline-resistant organisms has resulted in a general decline in use of tetracyclines and tetracycline analogue compositions as antibiotics of choice.
The invention pertains, at least in part, to substituted tetracycline compounds of the formula (I): 
wherein:
X is CHC(R13Yxe2x80x2Y), CR6xe2x80x2R6, S, NR6, or O;
R2 is hydrogen, alkyl, alkynyl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, alkylamino, arylalkyl, aryl, heterocyclic, heteroaromatic or a prodrug moiety;
R4 and R4xe2x80x2 are each hydrogen, alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, alkylamino, arylalkyl, aryl, heterocyclic, heteroaromatic or a prodrug moiety;
R2xe2x80x2, R3, R10, R11 and R12 are each hydrogen or a pro-drug moiety;
R5 is hydrogen, hydroxyl, or a prodrug moiety;
R6, R6xe2x80x2, and R8 are each independently hydrogen, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, alkylamino, arylalkyl, or halogen;
R7 is hydrogen, dialkylamino, heteroaryl-amino, or NR7cC(xe2x95x90Wxe2x80x2)WR7a;
R13 is hydrogen, hydroxy, alkyl; alkenyl; alkynyl; alkoxy; alkylthio; alkylsulfinyl; alkylsulfonyl; alkylamino; or an arylalkyl;
Yxe2x80x2 and Y are each independently hydrogen, halogen, hydroxyl, cyano, sulfhydryl, amino, alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, alkylamino, or arylalkyl;
R9 is hydrogen, heteroaryl-amino, or NR9cC(xe2x95x90Zxe2x80x2)ZR9a;
Z is CR9dR9e, NR9b, or O;
Zxe2x80x2 is O or S;
R9a, R9b, R9c, R9d, and R9e are each independently hydrogen, alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, arylsulfonyl, alkoxycarbonyl, arylcarbonyl, alkylamino, arylalkyl, aryl, heterocyclic, heteroaromatic, absent, or a prodrug moiety, and R9d and R9e may be linked to form a ring;
W is CR7dR7e, NR7b or O;
Wxe2x80x2 is O or S; and
R7a, R7b, R7c, R7d, and R7e are each independently hydrogen, alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylsulfinyl, arylsulfonyl, alkoxycarbonyl, arylcarbonyl, alkylamino, arylalkyl, aryl, heterocyclic, heteroaromatic, absent, or a prodrug moiety, and R7d and R7e may be linked to form a ring;
and pharmaceutically acceptable salts thereof, provided that R9 is not hydrogen when R7 is dialkylamino or hydrogen.
The invention also pertains, at least in part, to methods for treating a tetracycline responsive state in a subject. The method includes administering to the subject a substituted tetracycline compound of formula (I).
In another embodiment, the invention includes pharmaceutical compositions comprising a therapeutically effective amount of a substituted tetracycline compound of formula (I) and a pharmaceutically acceptable carrier.
In yet another embodiment, the invention pertains to a method for synthesizing 7- and/or 9-substituted tetracycline compounds. The method includes contacting a tetracycline compound with a nitrating agent, under conditions such that a nitro tetracycline compound is formed, contacting the nitro tetracycline compound with a hydrogenating agent, under conditions such that an amino tetracycline compound is formed, and contacting the amino tetracycline compound with an amino reactive substrate, such that a 9- or 7-substituted tetracycline compound is formed.
The invention also pertains, at least in part, to a method for synthesizing a 7- and/or 9-substituted tetracycline compound of formula (I), by contacting a reactive intermediate with appropriate reagents under appropriate conditions, such that a substituted tetracycline compound of formula (I) is formed.
The reactive intermediate, wherein said reactive intermediate is of the formula: 
wherein:
X is CHC(R13Yxe2x80x2Y), CHR6, S, NR6, or O;
R2 is hydrogen, alkyl, alkynyl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, alkylamino, arylalkyl, aryl, heterocyclic, heteroaromatic or a prodrug moiety;
R4 and R4xe2x80x2 are each hydrogen, alkyl, alkenyl, alkynyl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, alkylamino, arylalkyl, aryl, heterocyclic, heteroaromatic or a prodrug moiety;
R2xe2x80x2, R3, R10, R11 and R12 are each hydrogen or a pro-drug moiety;
R5 is hydrogen, hydroxyl, or a prodrug moiety;
R6 and R8 are each independently hydrogen, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, alkylamino, or an arylalkyl;
R13 is hydrogen, hydroxy, alkyl; alkenyl; alkynyl; alkoxy; alkylthio; alkylsulfinyl; alkylsulfonyl; alkylamino; or an arylalkyl;
Yxe2x80x2 and Y are each independently hydrogen; halogen; hydroxyl; cyano, sulfhydryl; amino; alkyl; alkenyl; alkynyl; alkoxy; alkylthio; alkylsulfinyl; alkylsulfonyl; alkylamino; or an arylalkyl;
R7 is hydrogen, dialkylamino, thiourea, diazonium salt, thiocarboxamide, or nitro;
R9 is hydrogen, thiourea, diazonium salt, thiocarboxamide, or nitro; and pharmaceutically acceptable salts thereof, provided that R9 is not hydrogen when R7 is hydrogen or dialkylamino.